Hydraulic powered pneumatic super charger for on-board inert gas generating system

ABSTRACT

The inert gas generating system includes an air separation module (ASM) and a super charger. The ASM includes an ASM inlet configured for receiving an air flow, and an ASM outlet configured for expelling nitrogen enriched air (NEA). The super charger has a hydraulic system including a cylinder, a hydraulic piston housed within the cylinder, and a switching valve. The switching valve has a hydraulic fluid inlet, a hydraulic fluid outlet, and hydraulic passages fluidly coupling the switching valve to the cylinder near opposing ends of the cylinder. The switching valve is configured to alternate hydraulic fluid received at the fluid inlet between the hydraulic passages. The super charger also has a pneumatic system having identical pneumatic pistons coupled to opposing sides of the hydraulic piston, where each pneumatic piston is coupled to a pneumatic chamber having an air inlet and an air outlet coupled to the ASM inlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 60/586,842, filed Jul. 8, 2004, entitled “Hydraulic Powered Pneumatic Super Charger for On-Board Inert Gas Generating System”, which is hereby incorporated by reference for all purposes. This application is also related to the following issued patents, each of which is hereby incorporated by reference: U.S. Pat. No. 6,729,359, “Modular On-Board Inert Gas Generating System,” issued on May 4, 2004; and U.S. Pat. No. 6,739,359, “On-Board Inert Gas Generating System Optimization by Pressure Scheduling,” issued on May 25, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for improving aircraft safety. More specifically, this invention pertains to inert gas generating systems used on aircraft for preventing combustion in aircraft fuel tanks and cargo spaces. In particular, this invention relates to a super charger used to increase the air supply pressure to the air supply module of an inert gas generating system. The super charger transforms hydraulic power into pneumatic power, and provides an alternate air source for the inert gas generating system.

2. Description of Related Art

Military aircraft have used On-board Inert Gas Generating Systems (OBIGGS) for some years to protect against fuel tank explosions due to undesired phenomena, such as penetration from small arms fire. However, military aircraft are not the only aircraft that would benefit from OBIGGS. For example, investigations into the cause of recent air disasters have concluded that unknown sources may be responsible for fuel tank ignition and explosion. Subsequently, OBIGGS has been evaluated as a way to protect commercial aircraft against such fuel tank explosions started by unknown ignition sources.

OBIGGS protects against fuel tank explosions by replacing the potentially explosive fuel/air mixture above the fuel in the tanks (the ullage) with an inert gas, usually nitrogen. This nitrogen airflow, otherwise known as nitrogen enriched air (NEA), is generated by separating oxygen, otherwise know as oxygen enriched air (OEA), from local ambient air. The NEA is then pumped into the ullage. The device which separates the NEA from OEA is usually termed an Air Separation Module (ASM).

The performance of such OBIGGS systems, and their efficiencies are largely dependant on how well the ASM performs. For optimum performance, the ASM requires a compressed air supply to achieve efficient separation of NEA from OEA. In conventional OBIGGS systems, air supply for the ASM is obtained from engine bleed-air or from a rotary compressor. However, in extreme flight profiles, engine bleed-air may not be available to provide a supply of compressed air. Furthermore, during such extreme flight profiles, electrical power may not be available to drive a rotary compressor. In addition, a rotary compressor is inherently inefficient at transforming electrical energy into compressed air energy, thereby increasing fuel costs and diminishing performance of the OBIGGS.

Accordingly, an improved OBIGGS system that addresses the drawbacks of the prior art would be highly desirable. In particular, it would be advantageous to provide a compressed air supply that is not reliant on engine-bleed air or a rotary compressor. It would also be beneficial to provide such improvements with an efficient system that does not increase fuel costs or have other detrimental effects on the operation of the OBIGGS.

BRIEF SUMMARY OF THE INVENTION

According to the invention there is provided an inert gas generating system. The inert gas generating system includes an air separation module (ASM) and a super charger. The ASM includes an ASM inlet configured for receiving an air flow, and having an ASM outlet configured for expelling nitrogen enriched air (NEA). The super charger has a hydraulic system configured to be coupled to a hydraulic pressure differential, and a pneumatic system coupled to the hydraulic system. The pneumatic system is configured to supply the air flow to the air separation module.

The hydraulic system and the pneumatic system are isolated from each other to prevent contamination of the output air sent to the air separation module. The hydraulic system includes a cylinder, a hydraulic piston housed within the cylinder, and a switching valve. The switching valve has a hydraulic fluid inlet, a hydraulic fluid outlet, and hydraulic passages fluidly coupling the switching valve to the cylinder near opposing ends of the cylinder. The switching valve is configured to alternate hydraulic fluid received at the fluid inlet between the hydraulic passages.

The pneumatic system preferably comprises identical pneumatic pistons coupled to opposing sides of the hydraulic piston, where the pneumatic pistons are coupled to separate pneumatic chambers each having an air inlet and an air outlet coupled to the ASM inlet. Each pneumatic chamber may be a bellows or a pneumatic cylinder. The super charger also includes check valves at the air inlet and air outlet to prevent retrograde air flow.

Accordingly, the super charger improves the performance of the OBIGGS by providing a continuous supply of compressed air to the ASM, even under extreme flight conditions. In other words, the super charger is not reliant upon engine bleed air or an electrically powered rotary compressor. The supercharger can also provide an alternate air source for the OBIGGS system in the event that conventional systems fail. Furthermore, the super charger is easily adapted to operate with conventional OBIGGS systems.

In addition, the supercharger may be used as a source of compressed air wherever a source of hydraulic power is available.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a schematic cross-sectional side view of a hydraulic powered pneumatic super charger coupled to an ASM; and

FIG. 2 is a schematic cross-sectional side view of the hydraulic powered pneumatic super charger shown in FIG. 1.

Like reference numerals refer to the same components throughout the figures.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic cross-sectional side view of a hydraulic powered pneumatic super charger 100 (hereinafter “super charger 100”) coupled to an ASM 102. As explained in more detail below, a hydraulic pressure differential is applied to the super charger 100. This hydraulic pressure differential is then converted to a pneumatic pressure differential to draw local ambient air (inlet air) into the super charger 100 and to expel the now compressed air (outlet air) into an inlet 104 of the ASM. Subsequently, NEA is expelled from a first outlet 106 of the ASM 102, while OEA is expelled from a second outlet 108 of the ASM 102, as is well understood in the art and described in U.S. Pat. Nos. 6,729,359 and 6,739,359, which are incorporated herein by reference. The NEA may then be pumped into the ullage, cargo holds, or other spaces.

FIG. 2 is a schematic cross-sectional side view of the super charger 100 shown in FIG. 1. The super charger primarily has two systems, namely a hydraulic system (input) and a pneumatic system (output). The two systems are preferably completely fluidly isolated from one another so as to prevent contamination of the output air into the ASM inlet 104 (FIG. 1) by the hydraulic system. In other words, this separation ensures that the output air is clean and will not introduce contaminants into the inlet 104 (FIG. 1) that could cause deterioration of the ASM 102 (FIG. 1).

The hydraulic input system includes a switching valve 200 and a hydraulic piston 202 housed within a hydraulic cylinder or bore 204. The switching valve 200 includes two hydraulic passages 206A and 206B for supply and return of hydraulic fluid to and from the hydraulic cylinder 204. The switching valve 200 also includes a hydraulic fluid inlet 208A and a hydraulic fluid outlet 208B for receiving and expelling hydraulic fluid into and out of the switching valve 200, respectively.

The switching valve 200 is preferably configured to alternate hydraulic fluid received at the hydraulic fluid inlet 208A between the two hydraulic passages 206A and 206B and into the cylinder 204. Similarly, the switching valve 200 is preferably configured to alternate hydraulic fluid expelled from the cylinder 204 through one of the two hydraulic passages 206A and 206B and out of the hydraulic fluid outlet 208B. In a preferred embodiment, the hydraulic passage 206A is connected to a first side 210A of the cylinder 204 and the hydraulic passage 206B is connected to a second side 210B of the cylinder 204, i.e., separated by the piston 202.

The hydraulic piston 202 is directly coupled on each side to a pair of pneumatic pistons 214A and 214B, such as by pushrods 212A and 212B, respectively. In a preferred embodiment, the ratio between the surface area of the hydraulic piston 202 and the surface area of the pneumatic pistons 214A and 214B is sized to provide optimum pneumatic pressure. For example, if the aircraft hydraulic pressure is on the order of 3,000 psi and the pneumatic pressure desired is ideally on the order of 100 psi, then the ratio of the pneumatic to hydraulic piston surface area is approximately 30:1.

The pneumatic pistons 214A and 214B are attached to pneumatic chambers 216A and 216B, respectively. In some embodiments, the pneumatic chambers 216A and 216B comprise bellows 218A or 218B which compress and contract in phase with the movement of the pneumatic pistons 214A and 214B, respectively. In an alternative embodiment, the pneumatic pistons 214A and 214B are housed within their own pneumatic cylinders or bores. The pneumatic chambers 216A and 216B are provided with air supply inlets 222A and 222B, respectively. In a preferred embodiment, the air supply inlets 222A and 222B provide air to the pneumatic chambers 216A and 216B from the surrounding environment, such as ambient air collected by an air scoop or the like. The air supply inlets 222A and 222B also preferably have check valves 220A and 220B, respectively, to prevent backwards air flow during the compression cycle of the pneumatic chambers 216A and 216B.

The pneumatic chambers 216A and 216B also preferably have air supply outlets 226A and 226B, respectively. These air supply outlets 226A and 226B direct the pressurized air to the inlet 104 (FIG. 1) of the ASM 102 (FIG. 1). In some embodiments, the air supply outlets 226A and 226B, also have check valves 224A and 224B, respectively, to prevent backwards air flow during expansion of their respective pneumatic chambers 216A and 216B, respectively.

n use, pressurized hydraulic fluid from an aircraft hydraulic system (not shown) enters the hydraulic inlet 208A. The switching valve 200 directs the hydraulic fluid to a respective side, say 210A, of the cylinder 204. This creates a pressure differential on the opposing sides of the hydraulic piston 202 causing the hydraulic piston 202 to move in a first direction (upward in FIG. 2) to equalize this pressure differential. At the same time, the switching valve 200 expels hydraulic fluid from the other side 210B of the cylinder 204 and out of the other hydraulic outlet 208B. Thereafter, hydraulic fluid is supplied to the other side of the cylinder 210B by the switching valve, and the piston moves in a second direction opposing the first direction. In this way, hydraulic fluid pressure is continually supplied to the different hydraulic passages 206A or 206B to move the piston 202 back and forth.

Movement of the piston 202 causes movement of the pneumatic pistons 214A and 214B, thereby either compressing or expanding the pneumatic chambers 216A and 216B. When compressed, the air inside the pneumatic chambers 216A or 216B is forced out through the check valves 224A or 224B and though the air supply outlets 226A and 226B to the ASM 102 (FIG. 2). Similarly, when expanding, air is drawn into the pneumatic chambers 216A or 216B through the air supply inlets 222A and 222B and check valves 220A or 220B. While one pneumatic chamber is being compressed the other is expanding, i.e., the pneumatic system is symmetrical. As the compression/expansion strokes continue, the air flows through the ASM, thereby separating the NEA from the OEA and other constituents.

Accordingly, the super charger improves the performance of the OBIGGS by providing a continuous supply of compressed air to the ASM, even under extreme flight conditions. In other words, the super charger is not reliant upon engine bleed air or an electrically powered rotary compressor. The supercharger can also provide an alternate air source for the OBIGGS system in the event that conventional systems fail. Furthermore, the super charger is easily adapted to operate with conventional OBIGGS systems.

The foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously many modifications and variations are possible in view of the above teachings. For example, hydraulic pressure may be obtained from any one of multiple systems on board the aircraft, or a separate system could be provided for the operation of the super charger. In another example, the compressed air provided by the pneumatic chambers could be bled off to reduce the outlet pressure or provide pressure to other aircraft systems. Other embodiments may be advantageous for reasons of cost, fuel efficiency, safety, or the like.

The embodiments were chosen and described above in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents. 

1. An inert gas generating system comprising: an air separation module (ASM) having an ASM inlet configured for receiving a pressurized air flow, and having an ASM outlet configured for expelling nitrogen enriched air (NEA); a super charger comprising: a hydraulic system configured to be coupled to a hydraulic pressure differential; and a pneumatic system coupled to said hydraulic system, where said pneumatic system is configured to supply said air flow to said ASM.
 2. The inert gas generating system of claim 1, wherein said hydraulic system and said pneumatic system are fluidly isolated from each other so as to prevent contamination of the output air to the air separation module.
 3. The inert gas generating system of claim 1, wherein said hydraulic system comprises: a cylinder; a hydraulic piston housed within said cylinder; and a switching valve having a hydraulic fluid inlet, a hydraulic fluid outlet, and hydraulic passages fluidly coupling said switching valve to said cylinder near opposing ends of said cylinder, where said switching valve is configured to alternate hydraulic fluid received at said fluid inlet between said hydraulic passages.
 4. The inert gas generating system of claim 3, wherein said pneumatic system comprises identical pneumatic pistons coupled to opposing sides of said hydraulic piston, where each pneumatic piston is coupled to a pneumatic chamber having an air inlet and an air outlet, wherein said air outlet is coupled to said ASM inlet.
 5. The inert gas generating system of claim 4, wherein said pneumatic chamber is a bellows.
 6. The inert gas generating system of claim 4, wherein said pneumatic chamber is a pneumatic cylinder.
 7. The inert gas generating system of claim 4, further comprising a check valve in said air inlet for preventing airflow out of said pneumatic chamber.
 8. The inert gas generating system of claim 4, further comprising a check valve in said air outlet for preventing airflow into said pneumatic chamber.
 9. The inert gas generating system of claim 4, wherein a surface area of said hydraulic piston is sized to provide optimum pneumatic pressure.
 10. The inert gas generating system of claim 4, wherein a ratio of a surface area of said pneumatic piston to a surface area of said hydraulic piston is approximately 30:1.
 11. The inert gas generating system of claim 4, wherein ambient air is provided to each said pneumatic chamber.
 12. The inert gas generating system of claim 11, wherein the ambient air is collected by an air scoop.
 13. A hydraulic powered pneumatic super charger, comprising: a hydraulic cylinder; a hydraulic piston housed within said hydraulic cylinder; a switching valve having a hydraulic fluid inlet, a hydraulic fluid outlet, and hydraulic passages fluidly coupling said switching valve to said cylinder near opposing ends of said cylinder, where said switching valve is configured to alternate hydraulic fluid received at said fluid inlet between said hydraulic passages; and at least one pneumatic piston coupled to a side of said hydraulic piston, where said at least one pneumatic piston is coupled to a pneumatic chamber having an air inlet and an air outlet.
 14. The super charger of claim 13, wherein said hydraulic cylinder, said hydraulic piston, and said switching valve are fluidly isolated from said at least one pneumatic piston and said pneumatic chamber so as to prevent contamination of the output air to the air separation module.
 15. The super charger of claim 13, wherein said pneumatic chamber is a bellows.
 16. The super charger of claim 13, wherein said pneumatic chamber is a pneumatic cylinder.
 17. The super charger of claim 13, further comprising a check valve in said air inlet for preventing airflow out of said pneumatic chamber.
 18. The super charger of claim 13, further comprising a check valve in said air outlet for preventing airflow into said pneumatic chamber.
 19. The super charger of claim 13, wherein a surface area of said hydraulic piston is sized to provide optimum pneumatic pressure.
 20. The super charger of claim 13, wherein a ratio of a surface area of said pneumatic piston to a surface area of said hydraulic piston is approximately 30:1.
 21. The super charger of claim 13, wherein ambient air is provided to each said pneumatic chamber.
 22. The super charger of claim 21, wherein the ambient air is collected by an air scoop.
 23. A method of generating inert gas using an air separation module (ASM) having an ASM outlet configured for receiving an air flow and having an ASM outlet configured for expelling nitrogen enriched air (NEA), and a super charger having a hydraulic system and a pneumatic system coupled to said hydraulic system, where said pneumatic system is configured to supply said air flow to said ASM, the method comprising: receiving pressurized hydraulic fluid into a switching valve of said hydraulic system; directing said hydraulic fluid to a first side of a hydraulic cylinder connected to said switching valve by a hydraulic fluid inlet and a hydraulic fluid outlet; moving a hydraulic piston housed within said hydraulic cylinder into a first hydraulic piston position; moving a first pneumatic piston attached to a first side of said hydraulic piston to a first pneumatic position; contracting a first pneumatic chamber attached to said first pneumatic piston; receiving ambient air into the first pneumatic chamber; moving a second pneumatic piston attached to a second side of said hydraulic piston to a second pneumatic position; compressing a second pneumatic chamber attached to said second pneumatic piston; expelling pressurized air from said second pneumatic chamber into the ASM; expelling hydraulic fluid from a second side of said hydraulic cylinder; directing pressurized hydraulic fluid to said second side of said hydraulic cylinder; moving said hydraulic piston into a second hydraulic position; moving said second pneumatic piston to a third pneumatic position; contracting said second pneumatic chamber; receiving ambient air into said second pneumatic chamber; moving said first pneumatic piston to a fourth pneumatic position; compressing said first pneumatic chamber; expelling pressurized air from said first pneumatic chamber into the ASM; and expelling hydraulic fluid from said first side of said hydraulic cylinder.
 24. The method of claim 23, wherein said pneumatic chamber is a bellows.
 25. The method of claim 23, wherein said pneumatic chamber is a pneumatic cylinder.
 26. The method of claim 23, wherein said second and third receiving steps further comprise receiving ambient air through a first and second air inlet, respectively.
 27. The method of claim 26, wherein said first and second air inlets are fitted with check valves for preventing backflow out of said first and second pneumatic chambers.
 28. The method of claim 23, wherein said first and third expelling steps further comprise expelling pressurized air through a first and second air outlet, respectively.
 29. The method of claim 28, wherein said first and second air outlets are fitted with check valves for preventing backflow into said first and second pneumatic chambers.
 30. The method of claim 23, wherein a surface area of said hydraulic piston is sized to provide optimum pneumatic pressure.
 31. The method of claim 23, wherein ratios of surface areas of each said first and second pneumatic pistons to a surface area of said hydraulic piston is approximately 30:1.
 32. The method of claim 23, wherein said ambient air is collected by an air scoop. 